Court lines are used for defining the boundary of a court, and the rules of many playing activities are defined by court lines. Court lines are defined in many sports such as tennis or badminton to specify a service or return placement and the moving range of a player. The court line is not only just applied for determining whether a foul of a game occurs, but also can be utilized for conducting various analyses of sport games and make tactical plans; for instance, automatic score counting, and automatic mining of player's movement habits and styles. Obviously, the extraction, reconstruction, and analysis of the court lines have become essential techniques for sport event study.
The reconstruction and analysis of the court line are generally conducted through photo images taken by a camera. However, even in the same sport, the color of the photo images, the installation position of the camera, and the advertising vary with different courts. For example, the courts of tennis sport include red clay courts or blue hard courts. This increases the level of difficulty and complexity of reconstructing the court line from images significantly, and thus the court reconstruction has become a challengeable research subject.
In the conventional way of reconstructing the court line, the difference between the color of the court and the color of its advertising signs is used to binarize an image, and the position of a court line is found by horizontal projection. In another prior art, the court line is extracted by using the white dot recognition and main color recognition methods. However, if the color of the court and the color of the advertising background are the same but the different colors of materials, different brightness of the environment, and different installation positions of the camera will cause a failure of reconstructing the court line, and thus the conventional reconstruction of the court line is still not applicable for different environmental factors.
In view of the aforementioned problems of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct extensive researches and experiments, and finally provided a feasible solution to overcome the problems of the prior art.